Recording the birth and death of a single phonon

When light interacts with a crystal or a molecule, it can transfer energy to and from microscopic vibrations of their constituent atoms. The total energy is conserved, so that the difference in energy between the incoming and outgoing light equals the vibrational energy deposited in or recovered from the material. Physicists in Basel and Lausanne have developed a new technique to measure in real time the creation and destruction of individual quanta of vibrational energy (phonons) using ultra-short laser pulses and single photon detectors. They recorded the birth and death of single phonons in diamond and their technique can be applied to many different Raman active vibrational modes opening the way for detecting exotic vibrational quantum states such as entangled states where energy is delocalised over several vibrational modes. These results have been published in Physical Review Letters and selected as an Editor’s suggestion.